The revelation raised fresh questions about the independence of witnesses who have appeared in the trial, in which the billionaire tycoon is accused of abuse of office and paying to have sex with an alleged under age prostitute, an erotic dancer nicknamed Ruby the Heart Stealer.

Mariano Apicella, who has been described as Mr Berlusconi's personal "minstrel", testified during a hearing last Friday that he never saw the then prime minister "grope" or lay his hands on female guests at his so-called "bunga bunga" parties.

Mr Apicella, who has recorded a number of albums of sentimental love songs with the former cruise ship crooner, told the court in Milan that nothing improper happened at the gatherings, which he described as "normal dinners where people danced, sang and chatted."

Now it has emerged that in June 2011, with the sex trial well under way, Mr Berlusconi bought an apartment owned by Mr Apicella for 280,000 euros (£227,000).

The four-room apartment – a far cry from Mr Berlusconi's sprawling villa on Sardinia's exclusive Costa Smeralda or his multi-million pound residences in Milan and Rome – is in Albano Laziale, a modest town in the hills outside Rome.